Liquid Crystals of Cellulosics: Fascinating Ordered Structures for the Design of Functional Material Systems

Abstract

This article surveys progress in both fundamental and applied research related to cellulosic liquid crystals, mainly of chiral nematic order. These liquid crystals are divided into two different classes, namely cellulosic macromolecules and cellulose nanocrystals (CNCs), depending on the mesogenic constituent. We start with a review of the fundamental and chiroptical characteristics of molecular liquid crystals of representative cellulose derivatives and then discuss recent efforts on the design and construction of functional material systems (such as stimulisensitive optical media and novel hybrids with minerals). These systems make use of the liquid crystalline molecular assembly of cellulosics. The survey of the other class of cellulosic liquid crystals deals with colloidal suspensions of CNCs obtained by acid hydrolysis of native cellulose fibers. Following the review of fundamental aspects related to the isotropic-anisotropic phase separation behavior of CNC suspensions, attention is directed to current applications of free-standing colored films, polymer composites reinforced with CNCs as mesofiller, and inorganic hybridizations using CNC chiral nematics as template. Some comments and the outlook for future explorations are also offered.

Pickering Emulsions Electrostatically Stabilized by Cellulose Nanocrystals

“…The surface charge of CNC is primarily controlled by the hydrolysis conditions. Higher acid concentration, reaction time and temperature produces CNC of higher surface charge as promoted by sulphuric acid diffusion into fibers (Nishio et al, 2016 ). Zeta-potential of CNC produced by sulphuric acid hydrolysis varies from −20 to −80 mV.…”

“…Zeta-potential of CNC produced by sulphuric acid hydrolysis varies from −20 to −80 mV. In contrast, if hydrochloric acid is used to produce CNC, the resulting CNC has almost no charge (Nishio et al, 2016 ).…”

Thermotropic liquid crystalline properties of (hydroxypropyl)cellulose derivatives with butyryl and heptafluorobutyryl substituents

“…Cellulosic polymers can form a liquid crystalline phase in a condensed fluid state because of the inherent semirigidity in the carbohydrate backbone (Fukuda et al 1994;Fukuda et al 1995;Gray 1994;Gray and Harkness 1994;Guo and Gray 1994;Nishio et al 2016;Zugenmaier 1994;Zugenmaier 1998). The supramolecular arrangement in the mesophase is mostly chiral nematic (synonymous with cholesteric), probably originating from a chiral nature (asymmetry) in the molecular structure.…”

“…The supramolecular arrangement in the mesophase is mostly chiral nematic (synonymous with cholesteric), probably originating from a chiral nature (asymmetry) in the molecular structure. (Hydroxypropyl)cellulose (HPC) is a familiar liquid-crystalline cellulose derivative and offers the chiral nematics in a variety of common solvents (Gilbert and Patton 1983;Gray 1983Gray , 1985Gray , 1994Guo and Gray 1994;Nishio 2006;Nishio et al 2016;Zugenmaier 1998). This type of mesophase often imparts a vivid color due to selective light reflection, when the supramolecular helical periodicity (i.e., pitch P) is comparable to wavelengths of visible light.…”

Phase transition identification of cellulose nanocrystal suspensions derived from various raw materials

“…They found that the important properties and characteristics of nanocellulose can be tuned by varying the fabrication strategies and the sources of cellulose . Since the chiral nematic orientation of acid‐hydrolyzed CNC suspensions was first reported, the influences of various conditions such as addition field, ionic strength, counterions, preparation conditions, and reaction conditions on the anisotropic chiral nematic liquid crystal behaviors of suspensions were widely investigated . The phase separation phenomenon of CNC suspensions could be observed when its concentration exceeded a critical value.…”